1. Field of the Invention
The invention relates to a bridge coupling for a hydrodynamic torque converter which provides a friction coupling between the impeller and the turbine of the hydrodynamic torque converter.
2. Description of the Related Art
Germian reference DE 44 32 624 A1 discloses a prior art bridge coupling on a hydrodynamic torque converter which comprises an axially deflectable piston and is connectable via friction linings to the converter housing. At least one cavity is provided on the friction lining for the passage of hydraulic fluid from the converter hydraulic circuit.
Cavities of this type may be produced in the friction lining by the removal of friction material from the locations where cavities are planned. The friction material may be removed by a mechanical, thermal or chemical process to the desired depth, even to a depth that corresponds to the thickness of the friction lining. A template which leaves only those locations where cavities are desired uncovered is placed on the friction surface of a friction lining for this removal purpose. The uncovered locations are then subjected to the mechanical, physical or chemical process to remove material. In this type of material removal to create cavities, material remnants are left in the transition area of the cavities. When the piston is disengaged and the friction lining is thus separated from the converter housing, the material remnants may still frictionally contact a friction surface, such as the connector housing, and thereby produce an undesired drag, moment. This reduces the efficiency of the converter in an undesired manner. Moreover, frictional heat is created.
Cavities of this type may also be produced by pure stamping in the friction lining. Although this method creates no material remnants that result in unwanted drag moment, the depth of the cavities is limited to a fraction of the friction lining thickness. The cavities can therefore allow only a low volume flow of coriveiter fluid, which limits the desired cooling effect.